I asked the engineer if I could keep the old box or transfer the content. They didn't tell me about any additional charges but they rang up their call centre and were given a code and then told me I could keep it at no further cost.
They also gave me an Ethernet cable which they said should be used to connect the old Tivo to the new Tivo, I would then see the old content in the new shows - which was clearly wrong.
Also, they did not actually complete the install of the TiVo 6 - the "wall garden" was down so they left and told me to do it myself later.
In my bill I've been charged twice for the install and it is not working.